Re: better understanding rdma-cm UNREACHABLE/ETIMEDOUT scheme

[Alex Rosenbaum <alexr-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 5/23/2013 1:31 PM, Alex Rosenbaum wrote:
> On 5/21/2013 6:24 PM, Hefty, Sean wrote:
>> My first guess is that the server isn't responding to new requests. - 
>> Sean 
>
> This is where we're looking now.
> Now testing on 17 server with 8 clients per server.
>
> When disabling all RDMA traffic in the test we get 100% RDMA 
> connection established. So at least we know this is not some 
> fundamental issue with our setup.
>
> Modifying our code to increasing the priority of RDMA connection 
> handling to be higher then the RDMA traffic (CQ completions handling) 
> we still see many UNREACHABLE events. But only after quite a few 
> client got connected and started pushing traffic (1GB RDMA WRITEs from 
> server to client).
>
> We are now adding code (via the conn_attr private data) to compare 
> timestamp between the rdma_conenct, RDMA_CM_EV_CONNECT_REQ, 
> rdma_accept and on the client events of UNREACHABLE or CONNECTED.
> We'll have better understand once we see these results.
>
> thanks,
>
> Alex
We found the peace of code that got the server to hang for so long, 
enough to causes the rdma_connect() to fail on the client side with 
retries with RDMA_CM_EVENT_UNREACHABLE(-TIMEDOUT)
OK, case closed.

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